If the lubricating oil turns black, do you need to replace it immediately?

发布时间：2022年03月14日 14:52

After being used for a period of time, lubricating oil tends to turn black. Some car owners mistakenly believe that this indicates the oil has severely deteriorated and thus replace it prematurely, leading to unnecessary waste. Typically, motor oils are formulated with detergents and dispersants designed to wash away the sticky film and black carbon deposits that accumulate on pistons. As a result, the color of the lubricating oil often darkens after some use—but this does not mean the oil has gone bad. So why does the color of lubricating oil turn black? Today, our editor will explain it to you.

　　After being used for a period of time, lubricating oil tends to turn black. Some car owners mistakenly believe that this indicates the oil has severely deteriorated and thus replace it prematurely, leading to unnecessary waste. Typically, motor oils are formulated with detergents and dispersants designed to wash away the sticky film and black carbon deposits that accumulate on pistons. As a result, the color of lubricating oil often darkens after some use—but this does not mean the oil has gone bad. So why does lubricating oil turn black? Today, our editor will explain it to you.

　　Does blackened lubricating oil need to be replaced?

　　First: High olefin and sulfur content in fuels (which easily lead to sludge formation in gasoline engines and carbon deposits in diesel engines) can accelerate the darkening of engine oil. Thus, fuel quality is a major source of oil darkening. Second: Different engine designs and operating conditions—such as frequent starts and stops—can easily cause gasoline engines to produce sludge and diesel engines to experience incomplete combustion, resulting in carbon deposits and blackening. Third: To counteract the effects caused by fuels and mechanical factors mentioned above, lubricants must include dispersants to prevent sludge or carbon deposits from forming varnish-like films on cylinder walls or accumulating inside the engine. The higher the quality of the lubricant, the better its dispersing ability; however, such high-quality oils tend to darken more quickly. Therefore, high-grade oils darken faster than lower-grade ones. Fourth: The formation of sludge and blackening of engine oil is also related to prolonged operation of the engine under heavy loads and at high temperatures, to failure to clean the engine and oil pan when changing the oil, and to the filtering efficiency of the oil filter.

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